There's nothing fishy about Durell's Scuba Dive - you couldn't do better for a straight-forward arcader, which, if short on pace and thrills, is at least thoroughgoing and requires no little skill.
Your four scuba divers (your four lives) have to dive from a boat, avoiding various nautical nasties like jelly fish and sharks, to find assorted oyster pearls. Dive deeper, avoid the orrible octopussy and you'll find further delights in clam shells. Beyond the second Kraken you'll gain an extra life, be able to seek much needed oxygen (else you'll just have to hold your breath) and start looking for the real pieces of eight in the three treasure chests.
The only thing this game really lacks is Jacqueline Bissett's wet T-shirt from The Deep. Get your fish fingers on this!